Introduction

‘Endoscopy’ simply refers to examining the inside of the body with a scope. Nowadays, we generally consider ‘endoscopy’ to be an examination of the gastrointestinal tract. Since the introduction of the flexible fiberoptic endoscopes in the 1960s, endoscopy has come a long way from the days of rigid sigmoidoscopy or rigid esophagoscopy. Modern endoscopes are used to carry out day-to-day diagnostic and therapeutic procedures of the gastrointestinal tract. For the purpose of this chapter, we will concentrate on flexible endoscopy.

Indications

Upper gastrointestinal tract (GI) endoscopy and lower gastrointestinal tract endoscopy means direct inspection of the esophagus, stomach, duodenum, small intestines and the colon using a flexible fiberoptic endoscope. A gastroscopy (aka esophago-gastroduodenoscopy or OGD) refers to the examination of the esophagus, stomach and duodenum, whereas enteroscopy refers to examination of the small intestines. Full examination of the colon to the cecum is known as colonoscopy, examination of just the left colon to the splenic flexure is known as flexible sigmoidoscopy.

Endoscopy and fluoroscopy can be used to investigate the GI tract, but there are advantages to endoscopy which may be taken into account when a clinician decides which test to request:

Both endoscopy and fluoroscopy complement each other in the assessment of the GI tract. Gastroscopy is the investigation of choice for upper GI investigation and colonoscopy often follows radiological investigation. It could be argued that endoscopy would be preferable in every case as the patient could have both diagnosis and treatment in a single test. However, in many hospitals, endoscopy services are overstretched and a barium enema is often a good first line test in selected patients. Endoscopy also carries a risk of morbidity and even mortality as discussed below.

Types of endoscopy

Therapeutic endoscopic procedures

The simplest procedure is a biopsy where small fragments of tissue are sampled using forceps that are passed down the endoscope. This type of biopsy is used for benign or malignant lesions or to sample mucosal abnormalities such as colitis (Figure 20.8, see color insert).

A hot biopsy utilizes the same tissue forceps but with the application of diathermy. This is mainly used to biopsy small sessile polyps less than 5 mm across. The advantage of diathermy is that it coagulates potentially friable tissue but also the heat destroys tissue. This has the effect of both biopsying and destroying the polyp at the same time.

Snare polypectomy is used for pedunculated polyps. This involves lassoing the polyp with an extendable wire loop. The wire loop is passed around the polyp stalk, pulled snug and diathermy is used to coagulate as the wire cuts through the tissue (Figure 20.9, see color insert). The polyp can then be retrieved with a variety of devices such as a basket. Argon beam (plasma) coagulation combines a jet (beam) of ionized argon gas and electrocoagulation to create rapid vaporization of tissue and coagulation with eschar formation. This can be used to destroy large carpeting rectal lesions in unfit patients or to ablate angiodysplasia, Barrett’s esophagus and gastric antral vascular ectasia (GAVE).

Endoscopic mucosal resection (EMR) is a technique proliferated in Japan for large mucosal as well as submucosal lesions. In its simplest form, a lesion can be raised by infiltration of adrenaline solution to create a pseudopolyp before the lesion is excised by snare polypectomy technique. Other variations involve using specialist attachments to the endoscope to remove lesions in a technique not too dissimilar to variceal banding (Soetikno et al., 2003).

Variceal banding, sclerotherapy and endoscopic clips are used to treat bleeding problems including esophageal varices, bleeding ulcers and angiodysplasia. Variceal banding involves fitting a cap pre-loaded with rubber bands to the end of the gastroscope that is connected to a firing mechanism. The varix is sucked into the cap before the rubber band is fired, resulting in ligation. Injection sclerotherapy involves injection of sclerosant or fibrin glue into the ulcer base/varices/lesion to stop bleeding or induce shrinkage of the lesion. Mechanical endoscopic clips can be applied to bleeding points to stop bleeding.

Dilatation and stent insertion can be carried out endoscopically for treating achalasia and strictures. Traditionally, dilatations have been done with Savoury-Gillard or Mallory bougies under semi-blinded or radiology control. Modern hydrostatic pneumatic balloons have allowed dilatation under direct vision and better control of the rate and extent of the dilatation (Figure 20.1). There is a risk of perforation associated with dilatations and the results have favored balloon dilatations over the other methods (Hernandez et al., 2000).

Percutaneous insertion of gastrostomy tube into the stomach is also widely used. This utilizes the gastroscope to distend the stomach with air and, using the transilluminated light as a target, a guide wire is inserted into the stomach and retrieved by the gastroscope. A gastrostomy tube can then be placed and positioned in the stomach via the mouth. This procedure is done under local anesthetic with or without sedation which obviates the need for a general anesthetic and formal surgery.

Complications of GI endoscopy

Endoscopy is a very safe procedure but, nonetheless, it is associated with its attendant risk and complications. Several large studies, including the National Confidential Enquiry into Patient Outcome and Death (2004), have highlighted cardiopulmonary and sedation-related complications as the major complications, together with a number of procedure-related complications.

The general complications include over-sedation that may induce respiratory depression with hypoxia, bleeding, perforation, hyper- or hypotension, aspiration, cardiac events including angina and myocardial infarction and strokes (Green, 2006). Cardiopulmonary complications account for 50% of serious morbidity and approximately 50% of all gastrointestinal endoscopy related deaths (Daneshmend et al., 1991). Respiratory depression from over-sedation from midazolam and opiates have an antidote in the form of flumazenil or naloxone, respectively, allowing the sedation to be reversed if an adverse event occurs (Bell and Quine, 2006).

The perforation risk in diagnostic gastroscopy is estimated to be 0.03%. Perforation can occur anywhere from the pharynx to the duodenum. This may be caused by pushing the gastroscope blindly, taking biopsy and esophageal tears from eosinophilic esophagitis. There is an increased perforation risk with all therapeutic procedures, e.g. dilatations, stent insertion, EMR and sclerotherapy. Mild bleeding following taking biopsy and polypectomy in the upper GI tract is not uncommon but major hemorrhage is rare. Bleeding (17%) is common after EMR, but the majority stop spontaneously without requiring further intervention. It is estimated that hemorrhage following EMR is approximately 2% (Riley and Alderson, 2006).

Perforation from colonoscopy is associated with greater risks than fluoroscopy. Full colonoscopy carries more risk than flexible sigmoidoscopy and therapeutic procedures produce more complications than diagnostic scopes. The main risks are perforation and bleeding (Epstein, 2006).

Perforation is rare following flexible sigmoidoscopy, but the risk increases with colonoscopy and/or therapeutic procedures. Perforation is more likely if transmural inflammation or ulceration is present and the risks are greater in the right colon where the bowel wall of the colon is thinner and subject to higher pressures (Epstein, 2006). Perforation rates have been quoted as 1.96 per 1000 procedures for colonoscopy and 0.88 per 1000 procedures for flexible sigmoidoscopy (Gatto et al., 2003) with similar figures of 1.9/1000 for 10 486 colonoscopy and 0.4/1000 out of 49 501 sigmoidoscopies (Anderson et al., 2000). However, the flexible sigmoidoscopy screening trial in the UK demonstrated a perforation rate of only one per 40 674 for flexible sigmoidoscopies and four out of 2131 colonoscopies (UK flexible screening trial investigators, 2002).

The perforation can be due either to direct trauma from the colonoscope or a thermal injury from diathermy and the diagnosis is often delayed (Hall et al., 2005; Epstein, 2006). If the bowel is perforated, free air may be seen on erect chest x-ray but a CT or contrast enema may be necessary to confirm the diagnosis. Some patients can be managed non-operatively as they have had full bowel preparation and hence have a clean colon limiting contamination, but others will require surgery. The surgery carried out depends on the extent of the injury and the bowel pathology. A resection ± stoma may be necessary or just oversewing of the perforation.

Barium enema, on the other hand, carries a risk of only one serious complication per 9000, perforation of the rectum in one in 25 000 and one death attributable to barium enema in one in 60 000 (Blakeborough et al., 1997).

Mild bleeding can occur after any biopsy or polypectomy with an incidence of 0.001–0.24% (Guidelines for Management of Colorectal Cancer, 2007). This is not usually severe and is usually self-limiting. More severe bleeding can occur after snare polypectomy, especially if the polyp has a thick stalk with a large vessel within it. Again, this is usually self-limiting but, if it persists or is severe, this can be treated endoscopically. Primary bleeding can be dealt with by coagulation, adrenaline injection or by applying a small metal clip to the bleeding vessel (endoclip).

As discussed above, colonoscopy is only complete if the cecum, or preferably the terminal ileum, is reached. Patients are usually warned during the consent process that an incomplete examination may occur. If it is recognized that the cecum has not been reached, a completion barium enema may be requested to examine the residual colon not inspected at colonoscopy.